A Stanford-led analysis of more than 9,000 Fitbit users found that each additional 1,000 daily steps was associated with an 8% lower risk of developing a kidney stone, adding everyday movement to established prevention measures such as hydration, adequate dietary calcium and reduced sodium intake.
By yourNEWS Media Newsroom
Walking more each day may be associated with a meaningfully lower risk of developing kidney stones, according to a Stanford-led study that used months of activity data collected directly from participants’ Fitbit devices rather than relying on people to remember and report their exercise habits.
Researchers analyzed 9,376 participants in the National Institutes of Health’s All of Us Research Program who had no previous history of kidney stones and had sufficient Fitbit step and heart-rate data available during a 180-day baseline period.
During follow-up, 103 participants, or about 1% of the study population, experienced a first recorded kidney stone event.
After accounting for demographic and clinical factors, researchers found that every additional 1,000 steps taken per day was associated with an approximately 8% lower hazard of developing a kidney stone. The adjusted hazard ratio was 0.92 for each additional 1,000 daily steps, with a 95% confidence interval of 0.86 to 0.99.
The study, published online in the Journal of Endourology in July, included researchers from Stanford University School of Medicine and the University of Illinois Urbana-Champaign. The findings provide unusually detailed evidence about physical activity and kidney stone risk because the researchers were able to examine continuously recorded wearable-device data over time.
Previous studies examining exercise and kidney stones have often depended on questionnaires asking people to estimate their physical activity. Wearable devices allow researchers to measure actual steps and activity patterns repeatedly, reducing problems associated with inaccurate recollection.
The findings nevertheless show an association, not proof that adding exactly 1,000 steps will directly prevent a kidney stone in an individual patient. The research was observational rather than a randomized clinical trial, meaning other characteristics of more active participants could contribute to some of the difference in risk.
Researchers also examined moderate-to-vigorous physical activity and sedentary behavior.
Greater amounts of moderate-to-vigorous activity showed a trend toward lower kidney stone risk, while sedentary time by itself was not significantly associated with the development of stones. That distinction suggests overall movement volume may be particularly important rather than simply reducing the number of hours spent sitting.
The study did not establish the precise biological mechanism responsible for the association.
Kidney stones develop when substances in urine become sufficiently concentrated to form crystals. Calcium oxalate stones are the most common type, although stones can also consist of calcium phosphate, uric acid, cystine or other materials.
Physical activity can influence body weight, metabolism, cardiovascular health and mineral regulation, all of which may potentially affect stone formation. The Stanford study, however, was designed to measure the relationship between activity and subsequent stone events rather than determine exactly how walking changes urine chemistry.
Hydration remains one of the most firmly established preventive measures.
When the body does not receive enough fluid, urine becomes more concentrated, allowing calcium, oxalate, uric acid and other substances involved in stone formation to reach higher concentrations.
The National Kidney Foundation recommends drinking enough fluid to maintain adequate urine production, with many people who form stones advised to produce approximately 2.5 liters of urine per day. Individual fluid needs can vary, particularly for people with kidney disease or other medical conditions.
Exercise therefore presents an important balance.
More daily movement may be beneficial, according to the Stanford findings, but vigorous exercise or prolonged activity in hot conditions can increase fluid loss through sweating. Failing to replace that lost fluid may make urine more concentrated and increase conditions favorable to stone formation.
The National Kidney Foundation specifically advises people to replace fluids lost through heavy exercise, saunas and hot weather.
Diet is another major component of prevention, but recommendations can sometimes appear counterintuitive.
People who develop calcium oxalate stones may assume that eliminating calcium is protective because calcium is part of the stone. Dietary calcium generally has the opposite effect.
Calcium consumed with meals can bind with oxalate in the digestive tract before oxalate reaches the kidneys, reducing the amount absorbed into the bloodstream and ultimately excreted in urine.
The National Kidney Foundation says most people with calcium kidney stones should obtain approximately 1,000 to 1,200 milligrams of calcium per day from food and warns that a low-calcium diet can increase the risk of calcium oxalate stones by about 50%.
Milk, yogurt, cheese and other calcium-containing foods can help meet that target, particularly when consumed with meals containing oxalate.
Sodium can work in the opposite direction.
Higher sodium intake causes the kidneys to excrete more calcium into urine, potentially increasing the amount available to form stones. Reducing excessive salt consumption is therefore frequently recommended for people prone to calcium stones.
Fruits and vegetables can also play a role because they supply potassium, magnesium, citrate and other compounds associated with healthier urine chemistry.
Citrate is particularly important because it can bind with calcium and inhibit crystal formation.
Lemon juice is sometimes recommended for people with low urinary citrate. About 4 fluid ounces of lemon juice mixed with water can increase urinary citrate and can raise urine pH, making urine less acidic. That approach is not appropriate for every stone former, however, because some people already have urine that is too alkaline.
That is one reason prevention strategies increasingly emphasize individualized testing rather than giving every patient the same diet.
People who have already passed a kidney stone face a substantial risk of another. The National Kidney Foundation estimates recurrence risk at approximately 50% to 75% over a lifetime after an initial stone.
A 24-hour urine collection can measure factors including urine volume, calcium, oxalate, citrate, sodium, uric acid and pH, helping physicians determine why an individual is forming stones.
For someone with abnormally high urinary oxalate, limiting particularly high-oxalate foods such as spinach, almonds or rhubarb may be appropriate. Someone with low citrate may instead benefit from additional fruits and vegetables, dietary adjustments or citrate treatment.
The type of stone also matters. Prevention strategies for calcium oxalate stones can differ from those used for uric acid, cystine or infection-related stones.
The Stanford findings add physical activity to that broader prevention picture.
The researchers concluded that long-term activity — particularly the total number of steps accumulated each day — was inversely associated with new kidney stone events and could represent a modifiable behavioral factor worth considering in prevention efforts.
The results do not establish a mandatory daily step target or demonstrate that walking alone can prevent kidney stones. They do suggest, however, that the difference between a relatively inactive day and one containing several thousand additional steps may have implications beyond cardiovascular fitness.
Combined with adequate hydration, appropriate dietary calcium, lower sodium intake and prevention strategies tailored to individual urine chemistry, ordinary daily movement may represent another practical tool for reducing kidney stone risk.
Source: Natural News
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